1. Field of the Invention
The present invention relates to a device for offsetting two prosthetic components that are connected to opposite ends of the present invention wherein the first prosthetic component is offsetable in both the anterior-posterior and the lateral-medial directions from the second prosthetic component a selected distance along a single offsetting axis.
2. Description of the Related Art
Sometimes, due to accidents, health problems, birth defects, etc., people 5 need to have a limb 6 amputated. The amputated limb 6 terminates in a stump 7. In general, a socket 10 can be formed for any particular stump 7. Those sockets 10 are well known in the art, and each socket 10 has a central axis 11.
Fortunately for people requiring a prosthetic limb, much advancement has been made in the field of prosthetic limbs. Patients now have many choices, including endoskeletal and exoskeletal prosthetic limbs. The present invention relates generally to endoskeletal prosthetic limbs. That is, limbs comprised of structural components and that may have an optional aesthetic outer shell.
In the case of a prosthetic leg and foot combination, it is desirable that the prosthetic components of the leg be in predetermined angular alignment with respect to the prosthetic components of the foot. This can be accomplished by using angular alignment devices. One device of this type is a pyramidal adapter for use with a fixed angle connector, and is manufactured by Otto Bock having part number 4R56. This device, as well as other alignment devices, may work well for their intended purpose, but their use carries with them some undesirable consequences. Notably, even if proper angular alignment of the lower components is achieved with these types of devices, the lower components may be offset from the upper components and from the person's residual limb in the lateral direction 15, the medial direction 16, the anterior direction 17 and/or the posterior direction 18.
The lower components can be out of alignment with the upper prosthetic components or the residual limb for other reasons as well. For example, the particular geometry of a person's limb 6 and stump 7 may cause the prosthetic components to be in an improper offset alignment, even if the prosthetics are connectable to the stump in a proper angular alignment.
The person's ability to comfortably walk can be compromised when the prosthetic components are in an offset alignment. One problem that occurs when the prosthetic components are offset is that the person's gait is affected. This is most prevalent when the prosthetic components are offset in either of the anterior or posterior direction.
Another problem associated with offset prosthetic components is that the person's weight may not be centered over the lowermost prosthetic components. This can affect not only the person's comfort, but also can cause unintended stress concentrations to develop within the prosthetic limb. This may lead to damage to or failure of the prosthetic limb.
Some advances have been made in attempting to overcome the drawbacks. For example, U.S. Pat. No. RE 36,521 to Hiemisch discloses a connecting part between leg prosthesis components. The connecting part has an adjusting element eccentrically positioned upon a rectangular flange. A user can select how to orient the flange with respect to the prosthesis components. However, there are only four possibilities that the flange can be oriented to with respect to a component connected to the flange. Hence, the connecting part provides for only limited adjustability, and provides for no adjustability other than due to the interfaces between the connecting part and the other prosthetic components.
A pair of components having dovetail connections is made by Hosmer Dorrance Corporation under the name Spectrum Alignment System. Examples of these components include a pyramid receiver with female dovetail for connecting to a pyramid receiver with male dovetail. A side shift screw is provided. The side shift screw has a head with a rib that rests in a groove in the female dovetail section. The threaded end of the screw is received within a hole in the male dovetail section. The screw head remains laterally stationary relative to the female dovetail section as the screw is twisted. However, the male dovetail section translates towards or away from the screw head as the screw is twisted, depending on which way the screw is twisted. Three screws and ball bearings are shown to guide the male end within the female end. The ball bearings are anti-friction devices that reduce friction between the female and male dovetail sections, which encourage movement of the male end within the female end when the side shift screw is twisted. The structural integrity of the dovetail connection is determined solely by the strength of the ribs on the screw head. If the screw head fails, the entire component could fail.
A further undesirable aspect of the Hossmer Dorrance Corporation components is that an adapter is needed to allow for adjustments to be made in both the lateral-medial directions and the anterior-posterior directions. In this regard, one pair of male and female dovetail components are needed for adjustment in each of the lateral-medial and anterior-posterior directions. These components are not shown to be capable of adjustment in the both the lateral-medial directions and the anterior-posterior directions by making an adjustment along a single axis.
A still further undesirable aspect of the Hossmer Dorrance Corporation components is that those components are not shown to be extendable or adjustable in a direction generally parallel to the longitudinal axis of the prosthetic components that they connect to. Due to this lack of adjustability, the Hossmer Dorrance Corporation components are incapable of being used to selectably adjust the length of a prosthetic limb. This may lead to unsatisfactory results unless the other components used in combination with the Hossmer Dorrance Corporation components are capable of making longitudinal adjustments, or unless the other components are exactly properly sized, so that the prosthetic limb will have a correct length.
Thus, there exists a need for an offset alignment device that solves these and other problems.